During a first manufacturing process of a disc drive, a slider, a metal gimbal spring, a track accessing arm and a flex circuit are assembled together with one another to form an E block assembly. The flex circuit generally runs adjacent a length of the gimbal spring and is rigidly affixed at a rigid metal mounting tab that protrudes along the length of the gimbal spring. The rigid metal mounting tab limits undesired motion of the flex circuit due to windage.
Multiple electrical contact pads at the end of the flex circuit are bonded to transducer contacts. As part of the manufacturing process, springs in the slider suspension system are then mechanically adjusted, typically by bending as needed, to provide a desired nominal pitch static attitude (PSA) and roll static attitude (RSA) to ensure proper flight of the slider during use. After the mechanical adjustments, there is localized residual stress from the bending remaining in the flex circuit. The residual stress relaxes over time. The forces that the flex circuit exerts on the slider change unpredictably with time and the nominal PSA and RSA shift undesirably.
During a second manufacturing process, an E-block assembly is assembled with other disc drive components to form a completed disc drive. At room temperature, the slider flies at a desired fly height and at a desired pitch static angle in order to accurately read and write data from discs in the disc drives.
As the areal density of discs is increased, however, it is found that there is a need for tighter control of pitch static angle in order to accurately read and write data on the disc. It is found, however, that PSA and RSA are not stable, and change over time as the residual stress relaxes. The changes are so large that they are unacceptable for use with higher areal densities.
The changes in PSA and RSA are found to be larger after the disc drive is exposed to temperature and/or mechanical loading. Applicants have discovered that the higher temperatures increases stress relaxation in copper conductors in the flex circuit. Applicants have also discovered that the unstable PSA and RSA variations are exacerbated by a rigid mounting of the flex circuit to the metal spring. It appears that a rigid mounting undesirably limits the motion of the flex circuit during SA adjust process, increasing the load carried by the flex circuit struts which increases residual stress in the copper traces. Residual stress tends to relax over time, particularly after being exposed to additional thermal or mechanical loading, resulting in undesired changes in PSA and RSA.
A method and apparatus are needed to provide increased stability in pitch static angle, particularly after exposure to high temperatures or additional mechanical loading during assembly process, without losing the damping benefits of the mounting tab.
Embodiments of the present invention provide solutions to these and other problems, and offer other advantages over the prior art.